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| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 | /** * The main process: a scheme, a window, and a long list of things denied. * * This file adds no capability to the viewer. The renderer it loads is the same * bundle the website serves, reading the same files the same way; everything * here exists to give that bundle an origin it can live at and to close the * doors that a browser tab has closed already. Read it as a list of refusals * rather than a list of features — where a browser would show a permission * prompt, this says no without asking, because there is no feature above it * that would know what to do with a yes. * * `.cts`, not `.ts`: the package is `type: module`, `module: NodeNext` compiles * a `.cts` to a `.cjs`, and Electron's entry point has to be CommonJS. It also * gives `__dirname`, which is how the renderer directory is found. */ import { readFile } from 'node:fs/promises' import { join } from 'node:path' import { BrowserWindow, Menu, app, protocol, session, shell } from 'electron' import { buildMenu } from './menu.cjs' import { APP_INDEX, APP_ORIGIN, APP_SCHEME, CSP, contentType, resolveInside } from './protocol.cjs' /** * Where the renderer build is, relative to this compiled file. * * `dist-electron/main/main.cjs` → `dist-electron/renderer`. Inside an asar this * is a path within the archive, which `fs.readFile` understands natively — * that is one of the two reasons the handler reads rather than calling * `net.fetch`. The other is that reading leaves every response header ours to * set, and the CSP is a response header. */ const RENDERER_ROOT = join(__dirname, '..', 'renderer') /** * The window icon, which is a Linux-only concern and not a cosmetic one. * * macOS takes the icon from the bundle and Windows from the `.exe`; on both, * passing one here changes nothing. Linux is the exception: electron-builder * installs a hicolor ladder and a `.desktop` entry, and the *window* is still * drawn by the compositor from whatever the process itself declares — so * without this the app appears correctly in the launcher and generically in the * taskbar and the alt-tab switcher, which are where a user actually looks. * * Two paths because the file lives in two places. Packaged, it is an * `extraResources` entry beside the asar rather than inside it: `BrowserWindow` * hands the path to the platform, which is not going to read an archive. * Unpackaged, `__dirname` is `dist-electron/main`, so this reaches the * committed `build/icon.png` that electron-builder derives everything else * from — one drawing, both cases. * * A missing file is a warning on stderr and the default icon, not a crash, so * this cannot be the reason a launch fails. */ const WINDOW_ICON = app.isPackaged ? join(process.resourcesPath, 'icon.png') : join(__dirname, '..', '..', 'build', 'icon.png') /** * Register the scheme before anything else can ask about it. * * This must run at module top level: `registerSchemesAsPrivileged` is only read * during Chromium's startup, and calling it inside `whenReady` is too late — * the scheme registers, the app loads, and every privilege below is silently * absent. * * Each privilege earns its place: * * - **`standard`** is the one that keeps the app alive. Without it the page's * origin is opaque, `history.pushState` throws `SecurityError`, and * `ViewState.writeHash` has no handler above it — so the first navigation * into a genome kills the router, back/forward, and every deep link at once. * `localStorage` goes with it, taking the theme and every remembered table. * - **`secure`** makes it a secure context, which is what `crypto.subtle`, * module workers and wasm all require. * - **`supportFetchAPI`** so the renderer can `fetch` its own assets. * - **`stream`** for ranged and streamed responses. * - **`codeCache`** lets Chromium keep compiled JS between launches. The * bundle includes a 4.8 MB h5wasm chunk; this is the difference between a * cold start and a warm one. * * **`allowServiceWorkers` is deliberately absent**, and that absence is guard * three of three (see `src/pwa.ts`). A desktop build has no offline story to * tell — it is already on disk — and a worker here would buy nothing while * adding the one failure mode where an installed app serves a build the * installer replaced. */ protocol.registerSchemesAsPrivileged([ { scheme: APP_SCHEME, privileges: { standard: true, secure: true, supportFetchAPI: true, stream: true, codeCache: true, }, }, ]) /** * Sandbox every renderer, set before any of them exist. * * Belt to `sandbox: true`'s braces: that flag is per-window and someone will * add a second window one day. This is the process-wide default, so the new * window inherits it whether or not its author remembered. */ app.enableSandbox() /** * Answer a request on `app://`. * * The failure modes are all silent, so each is handled rather than allowed to * throw: an exception raised in here does not surface anywhere a user or a * developer will look — the renderer simply never receives a response, and the * window sits blank or half-loaded forever. */ async function handleAppRequest(request: Request): Promise<Response> { const url = new URL(request.url) // Only this origin. The scheme has exactly one host by design, and a request // for `app://something-else/` is either a bug or an attempt to reach a second // storage bucket under a name that looks like ours. if (`${url.protocol}//${url.host}` !== APP_ORIGIN) { return new Response('Not found', { status: 404 }) } // The root is the document. Only the root: a general "serve index.html for // any directory" rule is how a typo becomes a silently-served shell instead // of a 404, and this app has no path-based routes to need it — the router // lives entirely in the hash. const pathname = url.pathname === '/' ? '/index.html' : url.pathname const file = resolveInside(RENDERER_ROOT, pathname) if (file === null) return new Response('Forbidden', { status: 403 }) let body: Buffer try { body = await readFile(file) } catch { // Includes the directory case, which reads as EISDIR rather than ENOENT. return new Response('Not found', { status: 404 }) } return new Response(body, { status: 200, headers: { 'content-type': contentType(file), 'content-security-policy': CSP, // Take the declared type literally. The table in `protocol.cts` is short, // so anything unrecognised is served as bytes, and sniffing a `.metacool` // into something executable is a category of surprise worth closing. 'x-content-type-options': 'nosniff', // No `Cross-Origin-Embedder-Policy` here, deliberately. `require-corp` // looks like free hardening and is not: it also governs *cross*-origin // subresources, and every remote file this app opens is one — a bucket // that answers ranged GETs correctly but sends no `Cross-Origin-Resource- // Policy` header would start failing, at the byte layer, in a build where // the same URL works on the website. Not worth it for a page that already // embeds nothing and is framed by nothing (`frame-ancestors 'none'`). }, }) } /** * Whether a file-system permission is the app reading what the user chose. * * The page's own origin, and read access: a request from anywhere else -- a * page this window should never have navigated to -- or for writing is refused, * as every other permission is. `fileAccessType` absent is a request that has * not said, which is treated as the narrower of the two. */ function readsOwnFile(url: string, access: 'readable' | 'writable' | undefined): boolean { return url.startsWith(`${APP_ORIGIN}/`) && access !== 'writable' } /** * Ask remote hosts not to compress, which is the one thing this build can do * that a browser cannot. * * `Accept-Encoding` is a **forbidden header name** in Fetch, so no page can set * it — not with `fetch`, not with `XMLHttpRequest`. `RemoteRangeSource` says so * at its own line 128 and calls the caller's only recourse "stop using ranges". * The main process has no forbidden-header list, and that asymmetry is the * entire capability. * * **What it actually buys, measured rather than assumed.** Against a host that * gzips `application/octet-stream`, with the override off and on: * * | request | off | on | * |--------------------------|----------------------------------|------------| * | `HEAD` — the open probe | `gzip, deflate, br, zstd` → gzip | `identity` | * | `GET`, no range | `gzip, …` → gzip | `identity` | * | `GET`, **with** `Range` | **already `identity`** | `identity` | * * The last row is the one that matters, and it is not what one would guess: * **Chromium already sends `identity` whenever a request carries a `Range` * header**, because it cannot inflate a partial response. So ranged reads were * never the problem in a browser engine, and an override sold on fixing them * would be a no-op documented as a feature. * * The `HEAD` is the problem. `RemoteRangeSource.open()` probes with one, it * carries no `Range`, so it is answered compressed — and the reader then refuses * to read the file in ranges, with `remote-compressed`, rather than trusting a * `content-length` that describes the gzip stream. That refusal is correct and * stays, and the website answers it by downloading the whole file instead, up * to 128 MiB encoded, refusing past that (`worker/sources.ts`). This simply * means the desktop build stops provoking it: the same file, on the same host, * is read here in ranges like any other. GitHub Pages is exactly such a host, * which is the case `RemoteRangeSource` documents as having no client-side fix * for ranges at all. * * Only http(s), and only the request headers: this states a preference on an * outgoing request and can change nothing else. In particular it is **not** an * `onHeadersReceived` hook injecting `Access-Control-Allow-Origin` — that is * rejected outright. Response headers cannot make a server produce partial * content, so it would fix none of the failures people expect it to; and the * worker's `?edges=` sidecar fetch takes an arbitrary user-supplied URL and * renders the result, which a blanket ACAO injection turns into a read-anything * primitive. * * If a network stack ever re-applies its own value, nothing breaks: the app * falls back to exactly today's behaviour with today's error text. Verified to * survive the reader's real path — a synchronous `XMLHttpRequest` inside a * same-origin module worker — and not only `fetch` from the document. */ function askForUncompressedTransfers(current: Electron.Session): void { current.webRequest.onBeforeSendHeaders((details, callback) => { if (!details.url.startsWith('http://') && !details.url.startsWith('https://')) { callback({ requestHeaders: details.requestHeaders }) return } callback({ requestHeaders: { ...details.requestHeaders, 'Accept-Encoding': 'identity' }, }) }) } function createWindow(): void { const window = new BrowserWindow({ width: 1440, height: 900, minWidth: 720, minHeight: 520, // The window exists before the document paints; showing it empty is a // white rectangle for as long as the bundle takes to parse. show: false, backgroundColor: '#ffffff', title: 'chromosomix', // Linux only; see WINDOW_ICON. `undefined` is what the option means by // "leave it to the platform", which is the right answer on the other two. icon: process.platform === 'linux' ? WINDOW_ICON : undefined, webPreferences: { // Two members wide, and CommonJS because a sandboxed preload cannot be // ESM. A window whose preload fails to load still works: `src/desktop.ts` // asks whether the bridge is there rather than assuming it, so the app // degrades to browser behaviour instead of throwing. preload: join(__dirname, 'preload.cjs'), // Isolates the page's JavaScript from any privileged code in the same // frame. Off, a preload's objects are reachable and mutable by the page, // which turns every one of them into an escape route. contextIsolation: true, // Off: with it on, the page gets `require` and the file system, and the // app's own privacy claim ("nothing you open here leaves this machine") // stops being a property of the code. nodeIntegration: false, // Off, and this one is not about security. `isNodeRuntime()` in the // reader worker decides which h5wasm filesystem path to take purely by // whether `process` exists. Leak Node into the worker and every file open // takes the wrong path and dies with a generic `not-hdf5` error hundreds // of frames from the cause -- while `mountTarget()` starts writing tens of // megabytes into TMPDIR on the way past. nodeIntegrationInWorker: false, // Renderer runs in an OS sandbox. Off, a renderer compromise is a // compromise of the user's account. sandbox: true, // `<webview>` is a second, differently-configured renderer that inherits // none of the above. Nothing in this app uses one. webviewTag: false, // Nothing here is a text field worth a dictionary, and it is a network // fetch on some platforms. spellcheck: false, // Available while developing, absent from what ships: a packaged app with // devtools is a debugging surface on a machine we do not control. devTools: !app.isPackaged, // `webSecurity` is never set. Turning it off disables the same-origin // policy and the CSP above along with it, which would make every refusal // in this file decorative. }, }) window.once('ready-to-show', () => window.show()) void window.loadURL(APP_INDEX) } /** * One instance, so two launches share a window rather than a storage bucket. * * Two processes on one `localStorage` is not a crash; it is the last writer * winning, which presents as settings that revert for no reason. */ if (!app.requestSingleInstanceLock()) { app.quit() } else { app.on('second-instance', () => { const [existing] = BrowserWindow.getAllWindows() if (existing === undefined) return if (existing.isMinimized()) existing.restore() existing.focus() }) /** * Applies to every renderer that will ever exist, including ones added later * by someone who did not read this file. */ app.on('web-contents-created', (_event, contents) => { // A link that would open a new window opens in the user's browser instead, // and only if it is http(s). `window.open` in a desktop app is otherwise a // frameless, preference-free window with no address bar -- a page that can // look like anything, including like this app. contents.setWindowOpenHandler(({ url }) => { if (url.startsWith('https://') || url.startsWith('http://')) { void shell.openExternal(url) } return { action: 'deny' } }) // The window itself never navigates away from its origin. This is the // un-bypassable half of the dropped-file guard: a file dropped outside the // dropzone would otherwise navigate the window to a binary blob, with no // address bar and no back button to return from. // // It does not fire for `pushState` or for hash changes, so the app's own // router is untouched by it. contents.on('will-navigate', (event, url) => { if (!url.startsWith(`${APP_ORIGIN}/`)) event.preventDefault() }) contents.on('will-attach-webview', (event) => event.preventDefault()) }) void app.whenReady().then(() => { protocol.handle(APP_SCHEME, handleAppRequest) // Everything a page can ask for, refused without asking the user. The // viewer needs none of it -- no camera, no microphone, no geolocation, no // notifications, no clipboard read, no USB, no serial -- and a prompt the // app has no reason to show is a prompt the user cannot evaluate. // // With one exception, and it is the app's own: **reading** a file or a // folder the user chose, from the app's own origin. The picker is the // user's answer -- they pointed at the folder -- and what this lets // through is the browser asking again, on the next launch, whether that // answer still stands: refused, a folder connected yesterday was dead // today, and a workspace naming its files could not find them (SPECS // §20.6). Never writing, and never for any other origin. // // All three, because they are asked in different circumstances and denying // one leaves the other two answering with their defaults. const current = session.defaultSession current.setPermissionRequestHandler((contents, permission, callback, details) => { callback( permission === 'fileSystem' && readsOwnFile(contents.getURL(), 'fileAccessType' in details ? details.fileAccessType : undefined), ) }) current.setPermissionCheckHandler( (_contents, permission, origin, details) => permission === 'fileSystem' && origin === APP_ORIGIN && details.fileAccessType !== 'writable', ) current.setDevicePermissionHandler(() => false) askForUncompressedTransfers(current) // Application-wide, and before the first window: on macOS the menu bar // belongs to the app rather than to a window, so building it per-window // would leave the app with no menu whenever no window has focus. Menu.setApplicationMenu(buildMenu()) createWindow() // macOS: the dock icon reopens a window after the last one is closed, // because on that platform the app is still running. app.on('activate', () => { if (BrowserWindow.getAllWindows().length === 0) createWindow() }) }) // Everywhere except macOS, closing the last window quits -- which is the // platform convention, and on the others an app with no windows and no menu // bar is a process the user cannot see or stop. app.on('window-all-closed', () => { if (process.platform !== 'darwin') app.quit() }) } |